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1.
O. López M. Cócera L. Coderch J. L. Parra A. de la Maza 《Colloid and polymer science》2002,280(4):352-357
The lytic interactions of the nonionic surfactant dodecyl maltoside (DM) with liposomes formed by a mixture of lipids modeling
the stratum corneum (SC) lipid composition were investigated. To this end, the surfactant to lipid molar ratios (Re) and the
normalized bilayer/aqueous phase partition coefficients (K) were determined by monitoring the changes in the static light-scattering
(SLS) of the system during solubilization. The fact that the free surfactant concentration was always similar to its critical
micelle concentration indicates that the liposome solubilization was mainly ruled by formation of mixed micelles. In addition,
the linear dependence established between the level of SLS and Re indicates a progressive incorporation of DM in the liposomes
as well as the progressive formation of mixed micelles. DM showed in all cases lower bilayer activity (higher Re values) and
greater affinity with vesicles (higher K values) than those reported for its interaction with phosphatidylcholine (PC) liposomes.
Thus, whereas the SC lipid liposomes were more resistant to the action of this surfactant, its degree of partitioning into
SC bilayers was higher throughout the solubilization process than that exhibited in PC vesicles. Comparison of the present
Re values with those reported for the lytic interaction of dodecyl glucoside (DG) with SC liposomes reveals that in the case
of DM the bilayer activity was more than three times higher than that for DG in spite of the identical alkyl chain length.
Received: 19 July 2001 Accepted: 10 October 2001 相似文献
2.
The interaction of a series of polyethoxylated octylphenols (ethylene oxide units average 8.5–20.0) with liposomes modeling
the stratum corneum (SC) lipid composition (40% ceramides, 25% cholesterol, 25% palmitic acid and 10% of cholesteryl sulfate)
was investigated. The surfactant/lipid molar ratios (Re) and the bilayer/aqueous-phase partition coefficients (K) were determined by monitoring the changes in the static light scattering of the system during solubilization. The fact that
free concentration for each surfactant tested was always similar to its critical micelle concentration (CMC) indi-cates that
the liposome solubilization was mainly ruled by the formation of mixed micelles. The Re and K para-meters for liposome saturation fell as the surfactant HLB increased. Thus, at this interaction step the higher the surfactant
HLB, the higher the ability of these surfactants to saturate SC liposomes and the lower their degree of partitioning into
liposomes. However, the maximum solubilizing ability was achieved at intermediate HLB values. Thus, the octylphenols with
20 and 12.5 ethylene oxide units showed, respectively, the highest power of saturation and solubilization of SC structures
in terms of the total surfactant amounts needed to produce these effects. Different trends in the interaction of these surfactants
with SC liposomes were observed when comparing the Re and K parameters with those reported for PC ones. Thus, whereas the SC liposomes were more resistant to the surfactant action,
the affinity of these surfactants with these bilayer structures was higher in all cases.
Received: 3 March 1997 Accepted: 22 May 1997 相似文献
3.
《Colloids and surfaces. A, Physicochemical and engineering aspects》2006,272(1-2):2-7
A fluorescence method was employed to study the solubilizing interactions of several sucrose esters with Dioctadecyldimethylammonium chloride small unilamellar vesicles. In this paper we studied four different alkyl esters of sucrose, saturation and solubilization concentrations (Csat and Csol), the ester–DODAC molar ratio (Re) and bilayer/aqueous partition coefficients (K) were measured by monitoring changes in laurdan generalized polarization values. A new critical surfactant concentration at lower values than saturation concentration was observed. All critical concentrations showed linear dependence with DODAC concentration. The decrease in the length of surfactant alkyl chain (upper cmc) led to an increase in its ability to saturate and solubilize vesicles and to a decrease in its bilayer affinity. Consequently the shorter alkyl chain (lauryl sucrose ester), the higher ability to saturate and solubilize the vesicles, whereas the longer chain (stearyl sucrose ester), exhibited the highest degree of partitioning into the vesicles. 相似文献
4.
The mechanisms governing the subsolubilizing and solubilizing interaction of sodium dodecyl sulphate (SDS)/Triton X-100 mixtures and phosphatidylcholine liposomes were investigated. Permeability alterations were detected as a change in 5(6)-carboxy-fluorescein (CF) released from the interior of vesicles and bilayer solubilization as a decrease in the static light-scattered by liposome suspensions. Three parameters were described as the effective surfactant/lipid molar ratios (Re) at which the surfactant system a) resulted in 50% of CF release (Re
50%CF); b) saturated the liposomes (Re
SAT;c) led to a complete solubilization of these structures (Re
SOL). From these parameters the corresponding surfactant partition coefficientsK
50%CF,K
SAT andK
SOL were determined. The free surfactant concentrationsS
W were lower than the mixed surfactant CMCs at subsolubilizing level, whereas they remained similar to these values during saturation and solubilization of bilayers in all cases. Although theRe increased as the mole fraction of the SDS rose (X
SDS), theK parameters showed a maximum atX
SDS values of about 0.6, 0.4 and 0.2 forK
50%CF,K
SAT andK
SOL respectively. Thus, the higher the surfactant contribution in surfactant/lipid system, the lower theX
SDS at which a maximum bilayer/water partitioning of mixed surfactant systems added took place and, consequently, the lower the influence of the SDS in this maximum bilayer/water partitioning.Abbreviations PC
Phosphatidylcholine
- PIPES
piperazine-1,4 bis (2-ethanesulphonic acid)
- SDS
sodium dodecyl sulphate
-
X
SDS
mole fraction of sodium dodecyl sulphate in the mixed system
- CF
5(6)-carboxyfluorescein
-
Re
effective surfactant/lipid molar ratio
-
Re
50%CF
effective surfactant/lipid molar ratio for 50% CF release
-
Re
SAT
effective surfactant/lipid molar ratio for bilayer saturation
-
Re
SOL
effective surfactant/lipid molar ratio for bilayer solubilization
-
S
W
surfactant concentration in the aqueous medium
-
S
W, 50%CF
surfactant concentration in the aqueous medium for 50% CF release
-
S
W, SAT
surfactant concentration in the aqueous medium for bilayer saturation
-
S
W, SOL
surfactant concentration in the aqueous medium for bilayer solubilization
-
S
B
surfactant concentration in the bilayers
-
K
bilayer/aqueous phase surfactant partition coefficient
-
K
50%CF
bilayer/aqueous phase surfactant partition coefficient for 50% CF release
-
K
SAT
bilayer/aqueous phase surfactant partition coefficient for bilayer saturation
-
K
SOL
bilayer/aqueous phase surfactant partition coefficient for bilayer solubilization
- PL
phospholipid TLC-FID, thin-layer chromatography/flame ionization detection system
- PI
polydispersity index
- CMC
critical micellar concentration
-
r
2
regression coefficient 相似文献
5.
Solubilization of phospholipid bilayers by C14-alkyl betaine/anionic mixed surfactant systems 总被引:1,自引:0,他引:1
The mechanisms governing the solubilizing interactions between zwitterionic/anionic mixed surfactant systems at different molar fractions of the zwitterionic surfactant (X
zwitter) and unilamellar liposomes were investigated. Solubilization was detected as a decrease in static lightscattering of liposome suspensions. Three parameters were regarded as corresponding to the effective surfactant/lipid molar ratios (Re) at which the surfactant system a) saturated the liposomesRe
sat; b) resulted in 50% solubilization of liposomesRe
50%, and c) led to a complete solubilization of these structuresRe
sol. These parameters corresponded to theRe at which light scattering stars to decrease, reaches 50% of the original value and shows no further decrease. From these parameters the surfactant partition coefficients for these three steps (K
sat,K
50% andK
sol) were also determined. The mixed systems were formed byN-tetradecyl-N, N-dimethylbetaine (C14-Bet) and sodium dodecyl sulphate (SDS) in PIPES buffer at pH 7.20. Liposomes were formed by egg phosphatidylcholine and phosphatidic acid (9:1 molar ratio). When the range ofX
zwitter was about 0.4–0.6Re andK parameters showed a maximum, whereas the critical micelle concentration (CMC) of these systems exhibited a minimum. Given that the ability of the surfactant systems to solubilize liposomes is inversely related toRe
sol, this capacity appeared to be directly correlated with the CMC of the systems. The progressive rise ofK during the process indicates that an increasing surfactant partition equilibrium governs the interaction process from the saturation until the solubilization of vesicles, the free surfactant concentration remaining almost constant with similar values to the CMC for each mixed system studied. 相似文献
6.
Solubilization of different zwitterionic phospholipid vesicles structures such as L--phosphatidylcholine (PC) and 1,2-didecanoyl-sn-glycero-3-phosphocholine (DPC) have been studied in aqueous bulk by using zwitterionic surfactant dimethylhexadecylammoniopropanesulfonate (HPS). This has been done by studying the aggregation of HPS in pure water and in the presence of 7–36 M of fixed concentrations of each lipid with the help of pyrene fluorescence intensity (I
1/I
3) measurements. The fluorescence measurements showed that HPS monomers undergo two kinds of aggregation process, which were identified by the three breaks in a plot of pyrene fluorescence versus HPS concentration. The first two breaks, C
1 and C
2, indicate the onset and completion of vesicle solubilization respectively, upon incorporation of HPS monomers into the vesicles and led to solubilization in the form of mixed micelles. This process was not clearly visible at low lipid concentration. We evaluated the partition coefficient (K), which defines the degree of partitioning of surfactant monomers into the vesicles with respect to the aqueous medium. A high K value of HPS-lipid aggregates indicates the stronger interactions between surfactant and lipid vesicles. The K values evaluated for PC and DPC are quite close to each other, which indicates that K values were independent of phospholipid chain length. 相似文献
7.
M. Cócera O. López L. Coderch J. L. Parra A. de la Maza 《Colloid and polymer science》2000,278(8):794-799
The role played by cholesteryl sulfate (Chol-sulf) in the solubilization of liposomes modeling the stratum corneum (SC) lipids
by sodium dodecyl sulfate (SDS) was studied. We determined the surfactant-to-lipid molar ratios and the bilayer/aqueous phase
surfactant partition coefficients of this interaction by varying the proportion of Chol-sulf, the relative proportions of
the others lipids remaining constant. These parameters were determined by monitoring the changes in the static light scattering
of the system during solubilization. The fact that the free surfactant concentration was always similar to its critical micelle
concentration indicates that the liposome solubilization was mainly ruled by the formation of mixed micelles. The SDS ability
to saturate and solubilize SC liposomes decreased as the proportion of Chol-sulf in the bilayers increased until a minimum
was reached for a Chol-sulf proportion of about 15%. Inversely, the SDS partitioning into liposomes (or affinity with these
bilayers) increased as the proportion of Chol-sulf increased until a maximum was reached at similar Chol-sulf proportions
(10–15%). Hence, in these Chol-sulf proportions (similar to that existing in the intercellular lipids, which was 10%) the
ability of SDS molecules to interact with liposomes exhibits a minimum despite their enhanced partitioning into liposomes.
These effects may be related to the reported dependencies of the level of Chol-sulf on the abnormalities in the skin barrier
function and on the SC intercellular cohesion.
Received: 12 October 1999 Accepted: 20 January 2000 相似文献
8.
The assembly properties of the nonionic surfactant Triton X-100 and phosphatidylcholine (PC) aggregates during the overall solubilization process of PC liposome were investigated. Permeability alterations were detected as a change in 5(6)-carboxyfluorescein (CF) released from the interior of vesicles and bilayer solubilization as a decrease in the static light scattered by liposome suspensions. A direct dependence was established between the bilayer/aqueous phase surfactant partition coefficients (K), the growth of vesicles and the leakage of entrapped CF in the initial interaction steps (surfactant to phospholipid molar ratioRe up to 0.2). These changes may be related to the increasing presence of surfactant molecules in the outer monolayer of vesicles. In theRe range 0.2–0.35 the coexistence of a low vesicle growth with a constant increase of CF release may be correlated with the decrease inK (increased rate of flip-flop of surfactant molecules). Furthermore, in theRe range between 0.64 and 2.0 (lytic levels) almost a linear dependence was detected between the composition of these aggregates (Re) and the decrease in both the surfactant-PC aggregate size and the static light scattered by the system. This dependence was not observed in the last solubilization steps (Re range 2.0–2.60) possibly due to the increased formation of mixed micelles in this interval. The fact that the free Triton X-100 concentration at sublytic and lytic levels showed respectively lower and similar values than its critical micelle concentration confirms that permeability alterations and solubilization were determined respectively by the action of surfactant monomer and by the formation of mixed micelles.Abbreviations PC
phosphatidylcholine
- PIPES
piperazine-1,4 bis(2-ethanesulphonic acid)
- TX-100
Triton X-100
- CF
5(6)-carboxyflucrescein
-
Re
enective surfactant/lipid molar ratio
-
Re
SAT
effective surfactant/lipid molar ratio for bilayer saturation
-
Re
SOL
enective surfactant/lipid molar ratio for bilayer solubilization
-
S
W
surfanctant concentration in the aqueous medium
-
S
B
surfactant concentration in the bilayers
-
S
T
total surfactant concentration
-
K
bilayer/aqueous phase surfactant partition coefficient
-
K
SAT
bilayer/aqneous phase surfactant partition coefficient for bilayer saturation
-
K
SOL
bilayer/aqueous phase surfactant partition coefficient for bilayer solubilization
-
PL
phospholipid
- TLC-FID
thinlayer chromatography/flame ionization detection system
- PI
polydispersity index
- CMC
critical micellar concentration
-
r
2
regression coefficient 相似文献
9.
A. de la Maza O. López M. Cócera L. Coderch J. L. Parra J. Guinea 《Colloid and polymer science》1999,277(12):1200-1204
The capacity of the glycoprotein (GP) excreted by Pseudoalteromonas antarctica NF3 to protect phosphatidylcholine (PC) liposomes against the action of Triton X-100 was studied in detail. Increasing amounts
of GP assembled with liposomes resulted in a linear increase in the effective surfactant-to-PC molar ratios needed to produce
the same alterations in liposomes and in a linear fall in the surfactant partitioning between the bilayer and the aqueous
phase. Thus, the higher the proportion of GP assembled with liposomes the lower the surfactant ability to alter the permeability
of vesicles and the lower its affinity with these bilayer structures. In addition, increasing GP proportions resulted in a
progressive increase in the free surfactant concentration (S
W) for the same surfactant–liposome interaction step. The fact that S
W was always lower than the surfactant critical micelle concentration indicates that the interaction was mainly ruled by the
action of surfactant monomers, regardless of the amount of GP assembled.
Received: 4 May 1999 Accepted in revised form: 6 July 1999 相似文献
10.
The mechanisms governing the solubilization of neutral or electrically charged unilamellar liposomes by a series of octylphenol polyethoxylated surfactants (average of ethylene oxide units between 8.5 and 20.0) were investigated. Solubilization was detected as a decrease in light-scattering of liposome suspensions. To this end, in accordance with the nomenclature adopted by Lichtenberg, three parameters were considered as corresponding to the effective surfactant/lipid molar ratios (Re) at which the surfactant (a) saturated the liposomesRe
sat; (b) resulted in a 50% solubilization of vesiclesRe
50% and (c) led to a total solubilization of liposomesRe
sol. These parameters, corresponded to theRe at which light scattering starts to decrease, reaches 50% of the original value and shows no further decrease.It is noteworthy that theRe
sat parameter decreases as the EO contents or the surfactant critical micellar concentration (CMC) increases. However, theRe
50% and theRe
sol parameters show the lowest values for the surfactant with 12.5 EO units in its molecular structure regardless of the electrical charge of the lipid bilayers. As a consequence, these last parameters are not linearly correlated with the CMC of these surfactants. The CMC values of the surfactant/lipid systems at 0.5 mM lipid concentration corresponded in all cases to the surfactant concentration at which liposomes were saturated by surfactants (S
sat). 相似文献
11.
Musarat Jan Aijaz Ahmad Dar Adil Amin Nuzhat Rehman Ghulam Mohammad Rather 《Colloid and polymer science》2007,285(6):631-640
The study is focused on evaluation of clouding phenomena of the aqueous single nonionic surfactant system Triton X-100 (TX-100)
and its mixed systems with anionic aerosol-OT (AOT) and cationic dodecylpyridinium chloride (DPC) in presence of hydrophobic
ions furnished by sodium salts of carboxylic acids, viz., sodium ethanoate, sodium propanoate, sodium butanoate, and sodium
hexanoate and the respective carboxylic acids [ethanoic acid, propanoic acid, butanoic acid, and hexanoic acid]. The influence
of salts on the cloud point (CP) has been explained on the basis of salt effect as well as the solubilization of higher alkyl
chain hydrophobic ions furnished by these salts. Moreover, the co- and counterion effect has been taken into account to explain
the variation of the CP in the mixed systems. However, the effect of acids on CP has been explained in the light of their
aqueous solubility and their partitioning ability between octanol and water as reflected by their K
OW values. 相似文献
12.
Paula Gomes Maria João Araújo Eduardo F. Marques Soraia Falcão Rodrigo O. Brito 《合成通讯》2013,43(12):2025-2036
Double-chained surfactants with potential biocompatibility have been prepared in high yields by lysine acylation with four natural saturated fatty acids (C6 to C12) and with cis-undec-5-enoic acid. The surfactants were found to assemble into nanotubules in aqueous medium and, when mixed with a commercial cationic surfactant, to spontaneously form liposomes. 相似文献
13.
I. A. Belousova I. V. Kapitanov A. E. Shumeiko A. V. Anikeev M. K. Turovskaya T. M. Zubareva B. V. Panchenko T. M. Prokop’eva A. F. Popov 《Theoretical and Experimental Chemistry》2010,46(4):225-232
1-Alkyl-3-(2-oximinopropyl)imidazolium chlorides were prepared with different alkyl chain lengths (Alk = C12H25, C14H29). Some physicochemical indices (CMC and pK
aapp) were determined. The reactivity of these compounds was studied in the dissociation of 4-nitrophenyl esters of diethylphosphonic,
diethylphosphoric, and toluenesulfonic acids. The times for 50% conversion of the substrates into reaction products decrease
in the series: C12H25 > C14H29 >C16H33. In selecting the direction of modification of the supernucleophilic functional surfactants, we should take into account
not only their hydrophobic properties but also the efficiency of substrate solubilization as well as the reactivity of the
oximate group in the surfactant micelles. 相似文献
14.
S. D. Christian E. E. Tucker J. F. Scamehorn H. Uchiyama 《Colloid and polymer science》1994,272(6):745-754
The interpretation of intramicellar solubilization data obtained from semi-equilibrium dialysis (SED) experiments is described, and methods are presented for determining equilibrium constants for the solubilization of organic species by aqueous surfactant solutions as well as activity coefficients of both the organic solute and the surfactant within the micelle. The solubilization equilibrium constant of an organic solute in an aqueous micellar solution (K) is defined as the ratio of the mole fraction of organic solute in the micellar pseudophase (X) to the concentration of the unsolubilized monomeric organic solute in the aqueous phase (c
0). Expressions compatible with the Gibbs-Duhem equation are used to represent the concentration dependence of activity coefficients of both the solubilizate and surfactant in the micellar pseudophase; the analysis leads to calculated values of the concentrations of free and intramicellar surfactant and organic solute in both compartments of the equilibrium dialysis cell. Solubilization equilibrium constants for many amphiphiles are well correlated by the simple expressionK=K
0(1-BX)2, whereB is an empirical constant andK
0 is the limiting value ofK asX approaches 0. 相似文献
15.
《Physics and Chemistry of Liquids》2012,50(1):15-24
The Kerr effect of the Xanthan (charged polyelectrolyte; 113 ppm)/DTAB (surfactant) mixture in aqueous solution was studied. The static Kerr constant (B) and mean relaxation times (τ) values as a function of surfactant concentration (CDTAB ) were determined. The observed birefringence (Δn) is not a linear function of the electric applied field (E 2). For small E values Δn grows with E 2 and at a certain field value the birefringence tends to saturate. The addition of small quantities of DTAB lowers B values with respect to the Kerr constant of Xanthan (113 ppm) aqueous solution. The relaxation time of the mixtures is linearly dependent on the applied field and it decreases when DTAB concentration increases. The importance of the equivalent point is signalled. It is supposed that the initial rigidity of the polyelectrolite decreases because of the surfactant addition. Conductivity (σ) values as a function of surfactant concentration are presented. 相似文献
16.
Magnetically Alignable Bicelles with Unprecedented Stability Using Tunable Surfactants Derived from Cholic Acid
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Ryoichi Matsui Dr. Noriyuki Uchida Dr. Masataka Ohtani Kuniyo Yamada Arisu Shigeta Prof. Dr. Izuru Kawamura Prof. Dr. Takuzo Aida Dr. Yasuhiro Ishida 《Chemphyschem》2016,17(23):3916-3922
Five novel surfactants were prepared by modifying the three hydroxy groups of sodium cholate with triethylene glycol chains endcapped with an amide ( SC‐C1 , SC‐ n C4 , and SC‐ n C5 ) or a carbamoyl group ( SC‐O n C4 and SC‐O t C4 ). The phase behavior of aqueous mixtures of these surfactants with 1,2‐dimyristoyl‐sn‐glycero‐3‐phosphatidylcholine (DMPC) was systematically studied by 31P NMR spectroscopy. The surfactants endcapped with carbamate groups ( SC‐O n C4 and SC‐O t C4 ) formed magnetically alignable bicelles over unprecedentedly wide ranges of conditions, in terms of temperature (from 21–23 to >90 °C), lipid/surfactant ratio (from 5 to 8), total lipid content (5–20 wt %), and lipid type [DMPC, 1,2‐dilauroyl‐sn‐glycero‐3‐phosphatidylcholine (DLPC), or 1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphatidylcholine (POPC)]. In conjunction with appropriate phospholipids, the carbamate‐endcapped surfactants afforded unique bicelles, characterized by exceptional thermal stabilities (from 0 to >90 °C), biomimetic lipid compositions (DMPC/POPC=25:75 to 50:50), and extremely large 2H quadrupole splittings (up to 71 Hz). 相似文献
17.
《Journal of Dispersion Science and Technology》2013,34(2-3):245-253
We report a solubilization enhancing effect of A-B-type silicone surfactants in microemulsions. The effect of added long-chain silicone surfactants, Si25C3EO51.6 (extended length≈21.8 nm) and Si14C3EO15.8 (extended length≈8.5 nm) on the solubilization capacity of C12EO5 (extended length≈3 nm)/water/dodecane microemulsion was investigated at the hydrophile-lipophile balance temperature at which a microemulsion (surfactant) phase containing equal weights of oil and water touches the three-phase body. The addition of silicone surfactants exhibits an enormous increase of the swelling of the middle phase primarily with an associated increase in the structural length scale of the microemulsion. The solubilization power increases with increasing x2 (mole fraction of silicone surfactants to the total surfactant) and going through a maximum it decreases, since a lamellar liquid crystal introduces in the multiphase region at low surfactant concentrations. The solubilization capacity reaches at the maximum to an almost equal level for different x2 values, 0.02 for Si25C3EO51.6 and 0.09 for Si14C3EO15.8. The solubilization power of the lamellar phase shows a similar trend with lower magnitude. 相似文献
18.
Qiang Wu Miao Du Tao Ye Yong-gang Shangguan Jian-ping Zhou Qiang Zheng 《Colloid and polymer science》2009,287(8):911-918
Interactions between anionic polyelectrolyte, poly(acrylic acid) (PAA), and cationic surfactant, alkyltrimethylammonium bromide
(C
n
TAB), were investigated by rheological measurements in semidilute PAA solution. The dependences of the rheological behavior
on the chain length of the surfactant, PAA neutralization degree, and temperature were discussed. The results revealed that
both dodecyl and cetyltrimethylammonium bromides (C12TAB and C16TAB) could increase the viscosity of PAA solution when the surfactant amounts surpassed a critical surfactant concentration
(C
c), and C
c of C16TAB was lower than that of C12TAB at same PAA neutralization degree. The increase of viscosity is attributed to the surfactant micelles bridging of the
polymer chains and confine the mobility PAA chain. On the other hand, it is found that the hydrogen bonding also played an
important role in the PAA–C
n
TAB system, especially in lower neutralization degree PAA solution, which results in the viscosity increase rapidly with the
added surfactant into lower neutralization degree PAA solution. 相似文献
19.
Hadi Beiginejad Ahmad Bagheri Leila Safdari Yekta Z. B. Nojini 《Journal of inclusion phenomena and macrocyclic chemistry》2010,67(3-4):247-252
Thermodynamics on inclusion complexation of β-cyclodextrin (β-CD) with n-alkylpyridinium chlorides (C n PC, n = 12, 14, 16) were measured by conductivity technique to evaluate the effects of chain length of C n PC and temperature. The data obtained indicate that inclusion complexes S(CD) and S(CD)2 had formed between surfactant and β-CD in aqueous solution. Investigation showed that the K 1 (first equilibrium constant) for S(CD) formation is greater than K 2 (second equilibrium constant) for S(CD)2 formation. It has been found that C12PC forms only the 1:1 complex, while C14PC and C16PC form 1:1 and 1:2 complexes. Thermodynamic parameters of the complexation, i.e. ΔG°, ΔH° and ΔS° have been also calculated. The large values of ΔG° indicate that complexation between surfactant and β-CD is very favorable. 相似文献
20.
Dr. Nuno Basilio Borja Gómez Prof. Luis Garcia‐Rio Vitor Francisco 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(14):4570-4576
The formation of mixed micelles composed of dodecyltrimethylammonium bromide (C12TAB) and a hexamethylated p‐sulfonatocalix[6]arene (SC6HM) was studied by several techniques. It was found that above the critical aggregation concentration the concentrations of free and micellized surfactant are strongly related to that of SC6HM. When there is free SC6HM in solution, the addition of C12TAB mainly results in an increase in the concentration of micellized surfactant, but when all SC6HM has been aggregated, the addition of C12TAB results in a substantial increase in the concentration of free surfactant in solution. When the concentration of free surfactant is equal to the critical micelle concentration of the pure system, a second independent aggregation process is observed. This aggregation behavior has many features that are similar to those of more complex systems that involve surfactants in the presence of oppositely charged polyelectrolytes. In this way, calixarenes can serve as simple models to mimic polyelectrolytes and to gain insight into the complex behavior displayed by these macromolecules. 相似文献